I'm reading the planetary economy rules, and some things seem a bit odd.

Firstly, on the civilization level calculations, it says Planet Surface Area, or PSA for short, is Planet Area times 222. Where does the figure 222 come from? A city, with the surrounding unbuildable area included, is 22^2 squares large, that's 484 squares. The concerning example first calculates PSA = 4 * 222 = 888, but in the end uses the figure 1936 where that 888 should be. 1936 is 4 * 484, though.

Secondly, in all of the Sum of EachN/Sum of EachM calculations, it is possible that no facility from the EachM list is present. What sort of methods are used to prevent divide by zero errors in these cases?

It had been 484 when I last looked, they changed it for some reason on the rules page. Perhaps it was a mistake by the person who typed up the rules page, mistaking a 22^2 for a 222. If it were 222, that would allow for CL greater than 1, since you can easily fill up more than 222 squares in a single city.

Another thing is the example they give there doesn't even match their defined CL.

Yep in those cases it should have a ^ in there (so 22^2 in this case). The equations that are used in the game are correct, just someone forgot to add them into the rules page equations. Or they got deleted accidentally.

Been brought up before (has anyone thought of checking back through other threads?) many times, and been brought to the devs attention I believe.